Laser engraving on uneven surfaces

Using a laser engraver to make intricate patterns is as easy as focusing your laser beam on your material of choice and letting the machine do the rest. But things can get pretty complicated when dealing with a material that is uneven like say, a mug, a wine bottle, or some other cylindrical item.

How do you laser engrave on uneven surfaces?

There are 4 main ways of laser engraving on uneven surfaces. You can use geometrical modeling, a spring-loaded tool, the G-code ripper application or a 3-axis laser engraver. Of these four methods, using a 3-axis laser engraver is the easiest and most efifcient method.  Lets have a look at each of these methods in more detail below.

1. Using geometrical modelling

Geometrical modeling is also known as 3D computer-aided design (CAD) modeling and it is typically used in engineering for representing real-life items as models. Usually, the system elements that are represented in the model must correspond with the components that are on the geometric model. CAD models are very versatile in that they can capture very fine details including the properties of the materials, the curvatures, etc.  

The 3D nature of CAD software will allow for an accurate representation of the curvatures on your laser engraving material. The main challenge with this solution is that you will have to get a perfect CAD model of your material. If you can manage to get the design right, your project is as good as done. There are lots of Computer-Aided Design software that you can use for your laser engraving projects. Here is a list of the most popular ones;

  • AutoCAD
  • CATIA
  • BobCAD
  • BobCAM
  • Mastercam
  • Inventor
  • Creo
  • Fusion 360
  • Draftsight
  • TurboCAD
  • Rhinoceros
  • Solidworks
  • SKethUp

2. Using a spring-loaded tool

Using a spring-loaded tool is an easier and faster way of engraving uneven surfaces. The spring-loaded tool makes engraving, marking, etching, and scribing of curved materials easier and more accurate. The tool was specially designed to take into account the variations that are typical of an uneven surface.

A spring-loaded tool works with all CNC laser engravers or any other laser machine that uses a 3/16-inch dia tool bit. The tool works by providing constant pressure on the engraving tool bit and this makes it possible to float within the tool holder which helps to compensate for the uneven surfaces. Here is a link to a good spring-loaded tool from Amazon which you can use for both power and drag engraving.

3.Using G-Code ripper

G-Code ripper is a little-known but very powerful software written in the Python programming language. The program is open source and so you can easily test it with your engraver without any cost. You can download the G-Code software for free from this link (The software only runs on windows). Once you have set it up, engraving on uneven surfaces is just a matter of following these easy steps;

  • Open the file in the G-Code ripper application
  • Enable splitting of the image by marking the “mid-center” of the image. You can achieve this by setting the split angle to 90 degrees
  • Rotate the black cuts to 180 degrees by selecting the “rotate black” setting and then save the “black” and “white” g-code files
  • Prepare your laser engraving machine and material
  • Engrave the first of the two images (black and white) that you had generated earlier. The order doesn’t matter.
  • Unmount the piece from the engraving table and rotate it 180 degrees from your original orientation
  • Engrave the second image that you generated earlier

If you have any issues in setting up your software, you can refer to the official documentation of the software which you can access via this link

4. Three-axis control

The main reason why engraving on curved surfaces is a challenge is the fact that most engravers only mark materials using the X and Y-axis. Thankfully, new technology has now made it possible to introduce a third axis – the Z-axis.

In this new technology, the laser head uses an expansion lens that is placed on a sliding electronic galvanometer to allow for the marking of materials on the Z-axis. This means that laser machines can now mark curved surfaces like cylinders, spheres, or even multi-tiered surfaces.

Most modern laser engravers now come with three-axis control but I recommend the CNC Router Kit (Amazon Link). You can use it to engrave a variety of materials including wood, acrylic, plastics, painted metal surfaces, etc.